Our ability to predict sea levels in the near future is contingent on our understanding of the processes responsible for flow of Antarctic ice streams and glaciers. Presently, the influence of tidal forcing on glacier movement is poorly understood. We are planning an experimental investigation of the dynamic frictional properties of periodically loaded ice sliding on rock. Since substantial accelerations and decelerations of glacial velocity are crucial to determining mass-balance and predictive models, an understanding of the source of such velocity changes is essential. Although the frictional strength of ice has been studied, to date these studies have all focused on constant rates of loading and sliding; No previous ice friction study has explored oscillatory stresses like those experienced by tidewater glaciers in nature. We will conduct laboratory experiments with a new, custom-fabricated low-temperature-friction apparatus (above) to systematically explore ice deformation under tidal loading conditions. We will determine the frequency and amplitude dependences of the ice frictional response and will measure directly the energy dissipation due to friction and anelasticity at conditions nearly identical to those experienced by Antarctic glaciers. This will advance our understanding of ice stream dynamics especially identifying the rheologic parameters responsible for the tidal response.

Photos (from top L)

1.Design of cryo-friction rig (currently under construction)

2.Selected glaciers in Antarctica that exhibit tidally modulated flow

3.cartoon of slider-block model of glacier flow, in which h(t) represents the changing tide height